The use of pluripotent cells has gained interest in medical research, particularly in the area of providing reagents for treating tissue damage either as a result of genetic defects, injuries, and/or disease processes. Ideally, cells that are capable of differentiating into the affected cell types could be transplanted into a subject in need thereof, where they would interact with the organ microenvironment and supply the necessary cell types to repair the injury. Embryonic stem (ES) cells are pluripotent cells derived from blastocysts that can be propagated indefinitely undifferentiated in vitro, can differentiate to all cell lineages in vivo, and can be induced to differentiate into most cell types in vitro (Martin, Proc Natl Acad Sci USA., 78:7634-7638 (1981)). Although ES cells have been isolated from humans, their use in research as well as therapeutics is encumbered by ethical considerations (Frankel, Science. 287:1397 (2000)
There have been increasing efforts to isolate stem cells from non-embryonic tissues, including hematopoietic (U.S. Pat. No. 5,750,397), neural, Gage, Science, 287:1433-1438 (2000), gastrointestinal, Potten, Philos Trans R Soc Lond B Biol Sci. 353:821-830 (1998), epidermal, (Watt, Philos Trans R Soc Lond B Biol Sci., 353:831-837 (1998), and mesenchymal stem cells (MSCs) (U.S. Pat. No. 5,736,396). Another population of cells, multipotent adult progenitor cells (MAPCs), has also been purified from bone marrow (Reyes et al., Blood, 98(9):2615-2625 (2001); Reyes & Vetfaillie, Ann NY Acad. Sci., 938:231-235 (2001)). These cells are capable of expansion in vitro for more than 100 population doublings without telomere shortening or the development of karyotypic abnormalities. MAPCs have also been shown to be able to differentiate under defined culture conditions into various mesenchymal cell types (e.g., osteoblasts, chondroblasts, adipocytes, and skeletal myoblasts), endothelium, neuroectoderm cells, and more recently, into hepatocytes (Schwartz et al., Clin Invest, 109:1291-1302 (2000)).
A challenge to the use of ES cells or other pluripotent cells for regenerative therapy in a subject is to control the growth and differentiation of the cells into the particular cell type required for treatment of a subject. As disclosed in Schuldiner et al., Proc Natl Acad Sci USA, 97:11307-11312 (2000), none of the eight growth factors used therein directed differentiation exclusively to one cell type. Thus, there continues to be a need for new approaches to generate populations of transplantable multi- and pluripotent cells suitable for a variety of applications, including treating injury and/or disease of various organs and/or tissues. Furthermore, sources of the multipotent or pluripotent cells are limited in that the cells must be harvested from living tissue.
U.S. Published Application Nos. 2004/0057942 and 2004/0033598 by Vacanti, et al., disclose small primitive cells which have an exceptionally high tolerance for oxygen deprivation. These cells, called “spore-like” cells, have been demonstrated to tolerate essentially complete oxygen deprivation for at least 24 hours (cells were viable despite oxygen deprivation for either four or 24 hours). Spore-like cells have a greater capacity to proliferate than terminally differentiated cells isolated from specialized tissues. Proliferative capacity is an important attribute because tissue engineering, cell therapies, and gene-based therapies are often hampered by physicians' inability to obtain sufficient numbers of cells to administer to a patient.
It is therefore an object of the present invention to provide subpopulations of spore-like cells expressing specific cell surface or gene expression markers.
It is also an object of this invention to provide a subpopulation of pluripotent spore-like cells, and a method for isolating a subpopulation of pluripotent spore-like cells.